Yamada C¹, Sawano K, Iwase N, Matsuoka M, Arakawa T, Nishida S, Fushinobu S.

J Gen Appl Microbiol. 2016 Nov 22. [Epub ahead of print]

Abstract

Two thermophilic bacterial strains, Bacillus thermoamylovorans NB501 and NB502, were isolated from a high-temperature aerobic fermentation reactor system that processes tofu refuse (okara) in the presence of used soybean oil. We cloned a lipase gene from strain NB501, which secretes a thermophilic lipase. The biochemical characteristics of the recombinant enzyme (Lip501r) were elucidated. Lip501r is monomeric in solution with an apparent molecular mass of 38 kDa on SDS-PAGE. The optimal pH and apparent optimal temperature of Lip501r were 8 and 60°C, respectively. Supplementation of 5 mM Ca²⁺ enhanced the thermostability, and the enzyme retained 56% of its activity for 30 min at 50°C. Lip501r was active on a wide range of substrates with different lengths of p-nitrophenyl (pNP) esters, and showed a remarkably higher activity with pNP-myristate. The K_m and V_max values for pNP-butyrate in the presence of 5 mM CaCl₂ were 1.8 mM and 220 units/mg, respectively. The possible industrial use of the thermophilic lipase in modifying edible oil was explored by examining the degradation of soybean oil. A TLC analysis of the degraded products indicated that Lip501r is an 1,3-position specific lipase. A homology modeling study revealed that helix α6 in the lid domain of NB501 lipase was shorter than that of lipases from the Geobacillus group.

See https://www.ncbi.nlm.nih.gov/pubmed/27885194